Studies demonstrate access to quality treatment and to psychosocial services can improve the lives of clients diagnosed with serious mental illnesses such as bipolar disorder and schizophrenia. Mental health professionals play an important role as they implement policies and procedures and provide access to services and to medications. Little is known about whether mental health professionals hold stigmatizing attitudes about people with mental illnesses, if these attitudes are related to their knowledge and skills in support of rehabilitation, or about the determinants of such attitudes. By contrast, a significant investment has been made to understand the prevalence and determinants of public conceptions of mental illness. This study proposes to compare the attitudes of mental health professionals to a national probability sample of adults (18 or older) living in non- institutional arrangements in the U.S. using case vignettes utilized in the 2006 mental health module of the General Social Survey (GSS). Innovative measures of unconscious or implicit social cognition were developed for this study to assess possible negative bias towards people with mental illness as mental health professionals may be particularly vulnerable to social desirability bias expressed in their attitudes about clients. We propose a secondary data analysis of individual and contextual determinants of potentially stigmatizing attitudes and of the skills and knowledge needed by mental health professionals to support rehabilitation. Data are from a 35 minute web-based survey of a representative sample of clinicians serving outpatient clients in Washington State's public mental health system. Seventy two percent of the agencies approached participated in the study and 862 staff responded, a 49.3% response rate. The survey contained the GSS case vignettes, two five minute Implicit Association Tests, designed using standard methodology to assess unconscious attitudes related to the competence and curability of individuals with mental illness relative to individuals with physical illness, and included a validated measure of treatment competencies. Mental health professionals were clustered within employment contexts that may be predictive of their knowledge, skills and attitudes. We also measured individual factors that may be associated with the attitudes of mental health professionals including their treatment credentials, employment and personal experiences with mental illness. The resulting research will contribute to understanding the prevalence and determinants of stigmatizing attitudes among mental health professionals. PUBLIC HEALTH RELEVANCE: This objective of this secondary data analysis project is to assess the prevalence and determinants of potentially stigmatizing attitudes held by mental health professionals to aide in the improvement of service delivery for clients with mental illness. Strengths include the significance of the topic, the well qualified research team.